Certain types of microelectronic devices are more vulnerable to chemical and mechanical damage than standard silicon semiconductors. For example many types of MEMS device have extremely fragile moving elements that can be destroyed by air currents. Surface Acoustic Wave (SAW) devices are fabricated with un-passivated aluminum metallisation and the frequency of operation will alter if the device is exposed to any polar liquid (including de-ionised water of the highest quality) and then dried off. Image sensors can have pixels obscured if particles fall on the active area of the die. For these devices there are advantages if the delicate member or area can be sealed in a protected environment as soon as possible after the wafer is completed. Various proposals have been advanced for attaching covers or lids to the wafer before severing the wafer to form individual chips. Despite all of this progress in the art, still further improvement would be desirable.